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Brilliant Lighting

Submitted by Robert on Sun, 12/11/2017 - 14:12

I make regular trips by bike along the Worcester and Birmingham canal tow-path. At this time of year I get reminded of the state of cycle lighting in this country, as I find myself trying to see where I'm going because someone coming in the opposite direction thinks the best approach is to imitate a lighthouse. Wrong. Have you ever seen a car with a bright flashing white light on its roof, beaming out light forwards, sideways, and into outer space? No. That's because such a light does nothing to help you see where you are going, and it dazzles oncoming vehicle operators. Also, it is difficult to judge the distance to a flashing light, which is not what you want when a motorist is trying to decide if they can move safely. The flashing is particularly problematic on an unlit path, where it will also induce motion sickness and possibly an epileptic seizure. The flashing light concept comes from the idea that a dim cycle light will be more noticeable if it flashes, but in fact it wont be noticeable at all if the vehicle behind has car headlamps. Modern lighting technology renders flashing front lights obsolete, because you can now buy good, bright, well-designed steady lights that don't get through batteries at an alarming rate. And they don't cost an arm and a leg, if you know what to look for.

The British standard for cycle lighting amounts to you must show a white light in the direction of travel, and it mustn't dazzle (it also permits a flashing light, within a certain frequency range). This is woefully inadequate. All the while we remain a member of the European Union, there is a far more detailed cycle lighting specification available to us, commonly known as StVZO. StVZO stands for Straßenverkehrs-Zulassungs-Ordnung, which translates as Road Traffic Licensing Regulations. The specification is sufficiently detailed to be used as a design specification for cycle lights, so if you buy an StVZO-compliant light and mount it correctly, it will illuminate your way without dazzling other users, and it will be bright enough that flashing is not necessary. In order to achieve this it will be designed to create a trapezoidal beam pattern that illuminates the road or path, but which doesn't shine into the eyes of an oncoming vehicle user. The British standard allows the use of a conical beam (like a torch), which will never be both bright enough to see by, and non-dazzling. Because the StVZO regulations have become the established norm across parts of continental Europe, and bike lights are fitted by law to bikes during manufacture, StVZO-compliant lights are commonly available and do not need to be expensive. In fact, I paid far less for a front light, a back light, a dynamo, and P&P from the Netherlands, than you will pay if you buy one of the front lights listed in the latest edition of the Cycling UK magazine. Without StVZO compliance, your only option is to read the reviews and judge manufacturer's marketing spiel and reputation. Bicubic lens? Sounds great, but does it help you see where you are going any better than any other lens? Computer-designed optics? Sounds good, but means nothing (everything is computer-designed these days, including my drawings below). Anti-dazzle beam technology? Sounds good, but how is that judged - nine out of ten cats can't be wrong? Without a meaningful standard, manufacturers can charge whatever they think they can get away with. Just because you spent lots of money on a light, that doesn't mean it will prove to be both effective and not anti-social.

So do yourself and others a favour, and get yourself at the very least an StVZO compliant front light. Better still, get yourself a set, complete with dynamo (and as Si Davies has pointed out on our Facebook page, BBB orange bikes are supplied with a hub dynamo). That means you will have great lighting bolted to your bike and ready for action at any time.

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Many so-called cycle lights for the British market produce a conical beam of light, like a torch. Typically the light beam will have a bright but narrow central cone, and a dimmer part that spreads out over a much wider angle. Most people then just mount this on their bike pointing straight ahead. This will shine directly into the eyes of oncoming vehicle operators (including other cyclists). They then cannot easily see where they are going. Additionally, since the beam is not illuminating the ground in front of you, you will think you need a more powerful light. By the time you have a light bright enough to see by, oncoming vehicle operators will be completely blinded until you have passed, and they will have poor night vision for some time after. Note that a large proportion of the light is wasted, illuminating things way above your head. This means reduced battery life (if you are using batteries).

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If you have a bright conical beam front light, you may have experienced shouted objections from oncoming cyclists. You might then be tempted to tilt the light downwards. Unfortunately the bright, narrow central cone will form a small bright spot on the ground. Beyond it you will see very little, because your eyes will adjust to the bright spot. Also, you may find that the outer cone of light is still too bright for oncoming vehicle operators. There is no good way to adjust a conical beam front light.

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Like motor vehicle lights, a properly designed cycle light has a trapezoidal beam. This directs most of the light in an even manner on to the road or path ahead of you. Beyond this the light cuts off rapidly, so it doesn't blind oncoming vehicle operators. A nice touch is that to get the beam right, you just point the light straight ahead (as best you can when fitting it), and then, once on the road at night, nudge it up or down a few degrees to fine tune it. The German StVZO specification calls for at least 10 lux of light (10 lumens/m²) in the area up to ten metres ahead of the bike (the yellow section in the drawing). The cut-off is defined as being no more than 2 lux 3.4 degrees above the main beam (the orange section in the drawing). There is no equivalent British specification. Within the European Union, the more tightly-defined German law trumps the British law. Even outside the European Union, the British law is so weakly defined that any StVZO compliant light will meet the British requirement. Since for many decades the British government has shown little interest in cycling as transport, that is unlikely to change. Alas that also means the problem of bad cycle lighting wont go away.
(https://blog.wheelies.co.uk/stvzo-approved-bike-lights/) (http://www.light-test.info/en/faq-en/169-stvzo-bike-lamps-regulations)

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If you adjust a trapezoidal beam front light so it is pointing too high, you will start to dazzle oncoming vehicle operators. However, unless you get it grossly wrong (by which point it will be completely useless for seeing by), it will still be less anti-social than a conical beam front light. If you point it too low, all that will happen is that you wont see much of the path or road ahead.

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Recent blog posts

The views expressed in blog posts do not necessarily represent Push Bikes policy, but they may influence that policy in the future. All posts appear on our Facebook page and you can make comments there if you wish. Alternatively please use the contact form on this website.